1. Field of the Invention
This invention relates generally geologic surveys and more particularly to an apparatus and method for acquiring and processing seismic data.
2. Description of the Related Art
Conventional geophone and hydrophone systems used in seismic prospecting typically have several sensors that produce signals indicative of a seismic wave. The seismic wave is usually produced by an energy source such as a vibrator truck, explosives or by an air gun in the case of a hydrophone system. These seismic signals are then conducted to acquisition/conversion circuitry. The analog signals from one or more remote seismic sensors (hydrophones, geophones, or other seismic sensors) are sampled and converted to a series of digital values by the acquisition/conversion circuitry. The acquisition/conversion circuitry is typically configurable to, for example, adjust the sampling rate, alter any digital filtering or other digital signal processing parameters, or perform diagnostics.
One or more of these acquisition/conversion circuits are connected to a data collection unit. Each data collection unit collects the series of digital values for all the seismic sensors connected to all the acquisition/conversion units connected to it. The data collection unit passes that data to a system controller, which may include a seismic recording device.
In the conventional system, the system controller initiates the entire system by enabling one or more power sources that provide power throughout the system. A common problem associated with powering a large system is known as galvanic corrosion. Galvanic corrosion occurs when dissimilar metals are provided a voltage potential while in an electrolytic environment. In seismic systems, the sensors, acquisition/conversion units, and usually the data collection units are in wet environments. As a result, the conventional system promotes galvanic corrosion whenever a unit or sensor is not connected at a connector terminal. This reduces the operational life of the connector thereby requiring maintenance at regular intervals.
Another drawback of the conventional system is the time required to recover from corrupted or otherwise unusable data packages transmitted from the data collection units to the main controller recorder.
Another drawback of the conventional system is in the inefficient rate at which data is transmitted alone the system line. Acquisition/conversion circuitry at a distal end of the system send less data over a longer distance of wire, while an acquisition/conversion unit closer to a data acquisition unit typically sends more data over a shorter distance. One skilled in the art would readily recognize that using single data rate for each of these acquisition/conversion units will limit the overall efficiency of the system.
Yet another problem with the conventional system is the centralized control of the system. A centralized controller must provide command and data control for the entire system regardless of the fact that in many instances only one unit may require control at a particular time.
The present invention addresses the above-identified problems found in the conventional seismic data acquisition system by providing a system having distributed control over the several units comprising the system. Additionally, the present invention provides an apparatus and method for efficiently controlling a seismic data acquisition system.
In one aspect of the present invention provides a seismic data acquisition apparatus comprising a first control unit, a second control unit coupled to the first control unit and to a plurality of seismic sensors, wherein the first control unit is adapted to sense at least one characteristic of the coupling between the first and second control units and to enable operation of the second control unit when the at least one characteristic meets at least one predetermined criterion.
Another aspect of the present invention is a seismic data acquisition system comprising a main control and recording unit, a first control unit coupled to the main control and recording unit a plurality of second control units coupled to the first control unit, wherein each of the plurality of second control units further comprises a seismic sensor coupled to a data acquisition unit and wherein the first control unit is adapted to sense at least one characteristic of the coupling between the first and second control units and to enable operation of the second control unit when the at least one characteristic meets at least one predetermined criterion.
Another aspect of the present invention is a seismic data acquisition apparatus, comprising a first data acquisition unit, a second data acquisition unit coupled to the first data acquisition unit, a power controller operatively associated with the first and second data acquisition units for controlling the propagation of power from the first data acquisition unit to the second data acquisition unit, a logic controller operatively associated with the first and second data acquisition units for controlling data processing and data transmission between the first and second data acquisition units, and at least one seismic sensor operatively associated with each of the first and second data acquisition units for sending a signal indicative of a formation characteristic to the first and second data acquisition units.
Another aspect of the present invention is a method of managing power in a seismic data acquisition system comprising first and second data acquisition units, the method comprising sensing a characteristic of a coupling between the first and second units using a controller in the first unit, and using the first unit to propagate power to the second unit when the characteristic substantially meets a predetermined criterion.